Better screen - retina thing is welcome but it's nothing to get excited about.
Bigger screen - I don't like big screened phones. If I want a big screen device, I'd get a tablet or something.
Faster CPU - that's why I have a 4S so it boots up faster than my iPhone 4 did. Why would I want a faster CPU for playing a few games and tweeting? Companies use "it's faster" as some kind of excuse when they have no major improvements.
Better camera - The 4S camera is ok for taking pictures and I'm happy with it but If I want a decent camera then I'll buy an actual camera.
I just want Apple to stop releasing the same thing every year. There is only so many times you can release the same iPhone with a slightly better processor, a better camera, little slimmer/lighter/bigger before people get sick of it.
Apple should come up with something to make people go "wow" again. I'm personally bored of the same old thing over and over. I know others probably are happy paying hundreds for virtually the same device every year but I'm not, hence why I'm happy on the 4S.